Last modified: 2014-11-17 09:21:30 UTC

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Bug 11259 - Djvu thumbnailing should dynamically select PNG or JPG
Djvu thumbnailing should dynamically select PNG or JPG
Status: NEW
Product: MediaWiki
Classification: Unclassified
DjVu (Other open bugs)
All All
: Low enhancement with 1 vote (vote)
: ---
Assigned To: Nobody - You can work on this!
Depends on:
Blocks: Wikisource
  Show dependency treegraph
Reported: 2007-09-09 15:51 UTC by Gregory Maxwell
Modified: 2014-11-17 09:21 UTC (History)
6 users (show)

See Also:
Web browser: ---
Mobile Platform: ---
Assignee Huggle Beta Tester: ---


Description Gregory Maxwell 2007-09-09 15:51:24 UTC
We currently use JPG images for Djvu thumbnails. This works out when the Djvu is continous-tone, but when the Djvu is bi-tonal images jpeg creates ugly artifacts and is larger than a 1bpp png would be.

Continous tone djvu data are compressed with the c44 wavelet codec. Bitonal images are compressed with the djvu jb2 codec. Pages can also be mixed mode.

If a page contains no c44 elements we should thumbnail that page with png, otherwise we should use jpeg. If controling the type on a page by page basis is too hard, then a document wide setting (all pages jb2?) would still be an improvement over what we have today.

The djvu tools easily extract the needed data:

djvudump SchindlerHouse_plans.djvu 
  FORM:DJVM [315634] 
    DIRM [90]         Document directory (bundled, 5 files 5 pages)
    FORM:DJVU [77924] {SchindlerHouse00001a.djvu}
      INFO [10]         DjVu 4820x3792, v24, 78 dpi, gamma=2.2
      Sjbz [77894]      JB2 bilevel data
    FORM:DJVU [71590] {SchindlerHouse00002a.djvu}
      INFO [10]         DjVu 4820x3792, v24, 78 dpi, gamma=2.2
      Sjbz [71560]      JB2 bilevel data
Comment 1 Bugmeister Bot 2011-08-19 19:12:32 UTC
Unassigning default assignments.

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